This invention relates generally to improved planetary gear systems. More particularly, but not by way of limitation, this invention relates to an improved planetary gear system for reducing speed and increasing torque from a drive axle that includes a face type coupling for preventing the rotation of the planetary gear carrier.
Planetary gear systems are not new. Insofar as applicant is aware, planetary gear systems have generally had the planetary carrier locked to the spindle against rotation through a spline connection. Wheel assemblies utilizing planetary gear systems of this type are utilized in a Caterpillar 988E loader and in Model FD-70500 planetary drive axles manufactured by Clark Equipment Co. An assembly of this type has also been utilized in the past by the assignee of this application in Models H400C and 570A wheel planetaries manufactured by International Hough Division of Dresser Industries, Inc.
While these arrangements have operated with reasonable success, they are subjected to extremely high loads and to sudden reversals of those loads. Spline connections are manufactured to include tolerances so that they can be assembled. The tolerances permit slight relative rotational movement and the reversal of loading, sometimes results in spline wear difficulties.
Gleeson Works of Rochester, N.Y. has developed a face type coupling which they market under the trademark "Curvic". Each part of the Curvic couplings includes a plurality of circumferentially spaced coupling teeth that are arranged to mate. The teeth are generally wedge shaped, in the axial direction and in a direction perpendicular to the axial center line or axis of the coupling. Accordingly, the coupling has the advantages of wedging tightly together when the coupling is engaged and retained in engagement and of being self-centering if properly applied.
Face type couplings have been utilized in axle assemblies as illustrated in U.S. Pat. No. 4,047,770, issued Sept. 13, 1977 to Korenhof et al. and in U.S. Pat. No. 4,352,528 issued Oct. 5, 1982 to Guimbretiere. While these are not necessarily the "Curvic" couplings, they are face type couplings. However, it is noted in those patents that the coupling arrangement is utilized for the purpose of transmitting rotation from the driving to the driven member and not for the purpose of locking a stationary member to prevent rotation.
An object of this invention is to provide an improved planetary gear system that obviates the disadvantages mentioned hereinbefore, that is, one that can be manufactured without the problem of tolerances that occurs with spline connections, one that is self-centering, and one that wedges together to prevent relative movement between the members of the coupling.